A .gov website belongs to an official government organization in the United States. A lock (LockA locked padlock) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. JavaScript appears to be disabled on this computer. Please click here to see any active alerts. PFAS (per- and polyfluoroalkyl substances) are widely used, long lasting chemicals, components of which break down very slowly over time. EPA's researchers and partners across the country are working hard to answer critical questions about PFAS. Environmental rules are codified under Title 40 of the Code of Federal Regulations (40 CFR). EPA helps regulated entities meet federal requirements, and holds entities legally accountable for violations. EPA issues guidance documents to further clarify and assist in implementation of regulations. Contact Us to ask a question, provide feedback, or report a problem.